docs: def clusters(self):
          """returns the clusters functions if supported in resources"""
          if self._resources is None:
              self.__init()
          if "clusters" in self._resources:
              url = self._url + "/clusters"
              return _clusters.Cluster(url=url,
                                       securityHandler=self._securityHandler,
                                       proxy_url=self._proxy_url,
                                       proxy_port=self._proxy_port,
                                       initialize=True)
          else:
              return None